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Aruba Networks has released the latest version of its WLAN system software, with several changes designed to optimize throughput even as the wireless network is flooded with mobile clients.

The company also says the new firmware release, ArubaOS 6.1.3.4, has features that speed recovery from network failures and maintain client application sessions for real-time applications, such as Microsoft Lync, videoconferencing and others.

In both cases, the changes are intended to make the enterprise WLAN more adaptable to changing spectrum conditions as the number of Wi-Fi clients soar, with smartphones and tablets. It's part of a major trend by WLAN vendors over the past 18 months to focus on WLAN features for improving RF spectrum management, signal quality and connectivity resilience.

The first set of changes is to Aruba's Adaptive Radio Management (ARM) software, an application that optimizes a battery of radio frequency features for enterprise wireless LANs.

What Aruba noticed, according to Ozer Dondurmacioglu, director of product marketing for the Sunnyvale, Calif., WLAN vendor, was an opportunity to mitigate a potential performance problem. If a Wi-Fi access point doesn't receive an acknowledgement from a client, it tries again to send the packets. But the access point picks a lower transmit rate for those retry packets, to make it more likely that they'll get through.

"The second try [therefore] takes up more airtime," Dondurmacioglu says. If this happens to, say 10-15% of the packets in an area with a lot of mobile Wi-Fi clients, "it can downgrade the total overall throughput for the access point and its associated clients," he says.

The software update counters this default behavior, and works to maintain higher re-transmit rates and the overall throughput for the access point.

A second change is an improved ARM algorithm that can distinguish between different types of 802.11n client radios, so they can be grouped together and given a fair share of the available airtime. For example, laptops might have high-performance 11n radios that support two or three data streams, with a potential data rate of 450Mbps; while 11n-equipped tablets have a radio with only one data stream, and a data rate of 65Mbps.

By grouping slower with slower and faster with faster, the latest ArubaOS firmware prevents slower clients from bogging down the faster ones. In turn, the faster clients spend less time on the radio link, freeing it up for reuse.

Aruba also improved the software's capabilities to speed up recovery from a network failure, including Wi-Fi clients being able to keep connections and application sessions. The faster recovery means clients don't drop their connection and start searching for a new SSID. From the end user's viewpoint, says Dondurmacioglu, "the Wi-Fi link never drops." TCP/IP applications "take a quick pause" and then continue to function. This is true even for time-sensitive applications like video conferencing, voice, and other real-time applications.

Aruba tested the new firmware released in a variety of settings, pitting the Aruba AP-135 against the Cisco 3602i access point, in a set of tests with a mix of Wi-Fi clients. Probably not surprising, the results show the Aruba gear maintaining higher throughput and capacity; dropping no Wi-Fi connections or real-time application sessions. The test report, with an explanation of the methodology used, is available online in PDF format.

The ArubaOS 6.1.3.4 release is available now, shipping with new hardware, and a free download to existing customers with support contracts.